luffy wanna kick ass all yonkou except shanks the man who inspired him to be pirate. also luffy still owe to shanks after saves him from sea monsters. maybe luffy like to beat shanks but it's like fairly match. who's stronger between them?, luffy will proved to shanks, he can become great pirate like his promise to shanks.
Shanks will get the hardest duel ever... Luffy will try even harder to beat him. It's all about pride, a man who once told a kid he would never become a pirate vs a kid driven by sheer motivation and starvation for food and of course that neet victory